Graphical Visualization of a Tree Growth Process Model
The Visualization Program: Tree Graphic Files
Although the usefulness of the Visualization Program centers on the interaction
between the user and the tree, it is sometimes helpful to have graphics
independent of the Geomview program. These graphics can be used as visual aids
in ECOPHYS presentations or for use in web pages.
Geomview
The first step in creating the picture is to generate the tree using the Visualization Program. The tree can then be
positioned with the Geomview
object manipulation tools until the desired view of the tree is found. The
size of the graphic can also be determined at this point by resizing the
Geomview camera window. As the window gets bigger, the tree will get bigger,
and vice-versa.
Snapshot
The next step is to take a "snapshot" of the tree graphic using a SGI program
appropriately named snapshot. This program does a screen capture of any portion
of the screen. By typing "snapshot" at the prompt, a small, button-shaped
window appears on the desktop. To take the picture, position the mouse cursor
over the snapshot button and hold down the "Ctrl" button. The mouse cursor
should now change into a camera icon. Next, move the camera to the top left-
hand corner of the portion of the screen that is to be captured and click and
hold down the mouse. Drag the mouse across the screen so that a red, unfilled
rectangle (called a rubberband) appears on the screen. When the rubberband surrounds
the desired portion of the screen, release the mouse. If the rubberband still
isn't exactly where you want it, right click on the snapshot window and choose
"Redraw Rubberband". Then, hold down the "Ctrl" key until the camera appears
again, and move it to the edge of the rubberband that needs to be changed. When
the camera is positioned on the edge, it will turn into a small, thin rectangle
that is aligned exactly as the edge. Now, just press down the mouse and drag
the line to the new position. Once the rubberband is right, the picture needs
to be saved into a file. If you don't want to use the default file name, right
click on the snapshot window, and select "New file name". A white input field
will appear over the window. With the mouse cursor positioned inside the field,
type in the new file name, ending with the extension .rgb. Finally,
save the picture by right clicking on the snapshot window and choosing "Save
scrn as filename", which will save the file in the current directory that
snapshot was loaded in.
XView
Jpegs and gifs are the most commonly used graphics formats, especially for web
pages. Because snapshot saves pictures in .rbg formats, the picture
must be converted. XView, a program found on the SGI's, is one such program
that will do this conversion. Typing "xv" at the unix prompt, then
right-clicking on the XView intro window, begins the program. Select "Load" and
choose the RGB file that contains the tree graphic. Next, select "Save" and
type in the name of the file to save it to (if it is different from the RGB file
name) and select the new file format.
File Formats
For pictures used on the World Wide Web, it may be better to save as a gif file.
There are only 255 colors allowed in gifs, which allows for smaller file sizes
(which are easier to load on web pages). In converting to 255 colors, the
original colors are replaced with one, or combinations of, the 255 colors that
is closest to it. This may cause some pictures to become pixilated. If this is
the case, programs such as Paint Shop Pro, Adobe PhotoShop, etc. can be used to
touch them up.
An extension to the gif format is animated gifs. These are graphics that, when
loaded in a web browser or on a web page, are animated. Animated gifs are
created much like cartoons are -- many pictures of an object in slightly
different positions are shown one after another, creating the appearance of
movement. To make an animated gif of an ECOPHYS tree, a small Geomview external
module was created, simply named Rotate Tree. By choosing this module from the
Geomview "External Modules" list, a form appears that asks for two parameters:
the name of the tree to rotate (as listed in the Geomview main panel under
"Targets") and number of turns it should take to rotate 360 degrees. To make
the tree turn, the button labeled "Rotate" is pressed. The tree will then turn
360/n degrees, where n is the number entered in the "Number of turns" field on
the form. For example, if the number "6" was chosen for the number of turns,
the "Rotate" button would have to be pressed six times in order for the tree to
rotate back to its original position. In between each rotation, the picture of
the tree should be captured as described above using snapshot. It is important
to remember not to change the size or position of the snapshot rubberband, or
the size and position of the tree in Geomview (other than the rotation),
otherwise the animated graphic will not look correct. Once all of the snapshots
are taken, convert them into the gif file format as described above. Then use
an image animation program such as Animation Shop included in Paint Shop Pro v5
to create the animated gif.
Next: Creating High Quality Graphics
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Author : Jennifer Messel,
jmessel1@d.umn.edu